You’re walking along the shoreline at low tide, the salt spray hits your face, and there it is. A bright orange or deep purple sea star, clinging to a rock or half-buried in the wet sand. Your first instinct might be to pick it up for a photo or to "save" it by tossing it back into the surf. But before you reach down, you need to understand the clock that starts ticking the second that animal hits the air. How long can a starfish survive out of water? For most species, we are talking about minutes, not hours.
It’s a fragile existence.
Sea stars—which scientists prefer over the name "starfish" because they aren't actually fish—are echinoderms. They don't have lungs. They don't even have gills in the way a salmon does. They breathe through a complex hydraulic system that relies entirely on constant immersion. When you pull them out of the ocean, you aren't just taking them out of their home; you’re effectively cutting off their oxygen supply and internal plumbing simultaneously.
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If you're looking for a hard number, most marine biologists, including experts from the National Oceanic and Atmospheric Administration (NOAA), suggest that many sea star species begin to suffer irreversible damage after just 3 to 5 minutes of air exposure.
Some can't even handle that.
The soft-bodied species, or those that live in deeper, cooler waters, are particularly vulnerable. When they are out of the water, they can't move. They can't regulate their internal pressure. They just sit there, slowly desiccating. It's a grisly way to go.
Sunlight is the enemy here. A sea star on a hot, windy day might only last a minute or two before its delicate tissues begin to dry out. Once the "skin" (the dermal branchiae) dries, the animal can no longer exchange gases. It suffocates in the open air. Imagine being submerged in a vat of thick syrup where you can't draw a breath; that’s roughly what it feels like for a starfish on a dry beach.
Why Air is Literally Toxic to Sea Stars
To understand why they die so fast, you have to look at how they work. Sea stars use a water vascular system. Instead of blood, they pump filtered seawater through their bodies to move their tube feet and transport nutrients.
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This system is open to the environment through a small, button-like structure on their top side called the madreporite.
When you lift a starfish out of the ocean, air can enter the madreporite. This is bad news. Bubbles in the water vascular system act like an embolism in a human. It creates a blockage. Even if you put the starfish back in the water ten seconds later, that air bubble might stay trapped inside, preventing the animal from moving its feet or circulating "blood." It might look fine when you drop it back in, but it could be dying a slow death on the seafloor because it can no longer function.
The Role of Desiccation and Stress
It isn't just about breathing. It's about chemistry. Sea stars are isotonic, meaning the salt concentration inside their bodies matches the water around them.
Air exposure causes rapid evaporation.
As water evaporates from the starfish's surface, the salt concentration in its remaining internal fluids spikes. This leads to osmotic shock. Their cells literally begin to shrivel. Furthermore, the stress of being handled causes them to produce mucus as a defense mechanism, which further depletes their energy reserves.
You might see them "stiffen" up. That's not them being tough. That's a stress response.
Species Differences: Not All Sea Stars Are Equal
Nature loves an exception. While a delicate deep-sea star will perish almost instantly, some intertidal species have evolved to handle the changing tides.
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- Pisaster ochraceus (Ochre Star): These are the hardy purple or orange ones you see on the West Coast of North America. They are built for the intertidal zone. They can survive several hours out of water during low tide by trapping moisture underneath their bodies and clinging tightly to cool, damp rocks.
- Common Starfish (Asterias rubens): Found in the Atlantic, these can handle short periods of exposure if the humidity is high, but they won't last long on a dry, sandy beach in the sun.
- Chocolate Chip Sea Stars: Often found in the pet trade, these tropical beauties are much more sensitive. Even a few minutes of air exposure during a tank cleaning can be fatal.
Humidity is the secret sauce. On a foggy, overcast morning at a tide pool, a sea star might survive a four-hour low tide because the air is saturated with moisture. On a 90-degree day in Florida? That same animal is toast in fifteen minutes.
The Problem with "The Selfie"
Social media has been a disaster for sea star populations in tourist heavy areas. People see a starfish, pick it up, hold it up to the sun for a photo, pass it to a friend, and then maybe—maybe—put it back.
By the time that photo is uploaded to Instagram, the starfish has likely crossed the point of no return.
Sunscreen is another silent killer. The oils and chemicals on human hands (oxybenzone, for example) are toxic to marine invertebrates. When you touch a sea star, you are transferring those chemicals directly onto its respiratory surfaces. It’s like someone rubbing poison onto your lungs.
Can You Save a Stranded Starfish?
Sometimes, you’ll find a sea star stranded high on the beach, far from the retreating tide. In this case, "saving" it is a noble goal, but you have to do it right.
- Check for life. Is it stiff or limp? If it’s crunchy and smells like rotting fish, it’s already gone. If it still has some flexibility, there's hope.
- Wet your hands first. Never touch a sea star with bone-dry hands. Use seawater to rinse your palms. Better yet, use a flat shell or a piece of driftwood to scoop it up so you don't touch it at all.
- No "throwing." Don't toss it like a frisbee into the waves. The impact with the water surface can damage its internal organs.
- Submerge it gently. Place it in a calm tide pool or back into the ocean in a spot where it can immediately cling to a rock or bury itself in the sand.
What the Experts Say
Marine biologists at the Monterey Bay Aquarium emphasize that the best way to interact with sea stars is to observe, not touch. They note that even the act of prying a sea star off a rock can tear its tube feet. Those feet are essential for its survival; without them, it can't eat mussels or hold its position against strong currents.
If it's stuck to a rock, leave it. It's there for a reason. It has likely trapped a pocket of water underneath itself to survive the low tide. By pulling it off, you break that seal and expose its vulnerable underside to the drying air.
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Misconceptions That Kill
There is a persistent myth that starfish can "breathe" air for a little while. They can't. They can only endure the lack of oxygen for a little while. It's a waiting game. They are holding their breath, metaphorically speaking, until the tide returns.
Another misconception is that they are "tough." Because they feel like sandpaper or hard plastic, people assume they are durable. In reality, they are complex biological machines with thousands of moving parts (tube feet) that are incredibly sensitive to pressure and chemistry changes.
The Ecological Stakes
Why does it matter if one starfish dies? Because they are keystone species.
The term was actually coined by ecologist Robert Paine while studying sea stars in Washington state. He discovered that when sea stars were removed from an ecosystem, the mussel population exploded and crowded out everything else, turning a diverse tide pool into a monoculture. When you kill a sea star for a photo, you are indirectly harming dozens of other species that rely on that sea star to keep the balance.
What to Do Next Time You're at the Beach
The fascination we feel for these creatures is natural. They look like something from another planet. But true appreciation involves respecting the biological boundaries of the animal.
- Stay in the "look but don't touch" zone. Use a waterproof camera or a GoPro to get close-up shots without removing them from the water.
- Educate others. If you see someone holding a sea star out of the water for an extended period, politely let them know that the animal is suffocating. Most people aren't trying to be cruel; they just don't know how the anatomy works.
- Watch the tides. If you want to see them in their natural habitat, check a tide chart and go during a "minus tide." You'll see them in the pools where they are happy, hydrated, and safe.
- Support marine conservation. Organizations like the Oceana or local reef preservation groups work to protect the habitats that these echinoderms need to survive.
Keeping a sea star in the water is the simplest thing you can do to ensure the ocean remains as vibrant and diverse as it should be. The next time you find yourself wondering how long that starfish can stay out of the water, remember: every second counts, and for the starfish, those seconds are a race against certain death.
Actionable Insights for Beachgoers:
- Observe the Madreporite: Look for the small, colorful dot on the top of the sea star—that's its life support intake. Keep it submerged.
- Minimal Handling: If you must move a stranded sea star, keep the total air exposure under 30 seconds.
- Choose the Right Spot: Always return a sea star to a shaded, wet area rather than direct sunlight or dry sand.
- Hands Off If Attached: If the animal is suctioned to a rock, prying it off will likely cause fatal injuries to its tube feet. Leave it where it is.